The Design of Rolling Bearing Mountings

31 Worm gear pairOperating dataInput power 3.7 kW; input speed 1,500 min –1 ; overallgear ratio 50:1.Bearing selectionWorm shaftThe worm shaft bearings are primarily axially loaded,the load direction changing with the direction of rotationof the worm. The radial loads acting on the bearingsare relatively small. A locating-flating bearingarrangement is selected.The locating bearing comprises two universal angularcontact ball bearings FAG 7310B.TVP.UA. Suffix UAindicates that the bearings can be mounted in any tandem,O or X arrangement. When the bearings arepaired in O or X arrangement and the shaft is machinedto j5 and the housing to J6, the bearings feature asmall clearance. The two angular contact ball bearingsare mounted in X arrangement. Depending on thedirection of rotation of the worm shaft, either one orthe other bearing accommodates the axial load.A cylindrical roller bearing FAG NU309E.TVP2 ismounted as the floating bearing.Worm gear shaftThe bearings of the worm gear shaft are mainly radiallyloaded; the axial loads are relatively low in comparison.A deep groove ball bearing FAG 6218 is thereforeprovided at the locating bearing end and a cylindricalroller bearing FAG NU218E.TVP2 at the floatingbearing end.Machining tolerancesAngular contact ball bearings: Shaft to j5; housing to J6Cylindrical roller bearings: Shaft to k5; housing to J6Deep groove ball bearing: Shaft to k5; housing to K6Lubrication, sealingThe worm gear and the bearings are oil-lubricated.The oil level should coincide with the lowest point ofthe worm teeth pitch circle diameter.The sealing rings at the shaft openings prevent oil fromescaping and offer adequate protection against contamination.31: Worm gear pair47 FAG